There are 40 pencils in a box. There are 15 pens in a packet. John gives one pencil and one pen to each person at a conference. He has no pencils or pens left. How many boxes of pencils and how many packets of pens did John buy?
Multiples of 15: 15, 30, 45, 60, 75, 90, 105, 120
Mulitples of 40: 40, 80, 120
This means that there are 120 people at the conference, and that he sold 3 boxes of pencils (40x3=120) and 8 boxes of pens (15x8=120)